The present invention relates to machines for the production of filter rods for use in the manufacture of filter plugs or filter rod sections in the making of filter tipped cigarettes, cigars or cigarillos. More particularly, the invention relates to improvements in apparatus which are utilized in filter rod making machines to apply a liquid plasticizer to successive increments of a continuously moving tow of filamentary filter material.
A filter rod making machine comprises an advancing mechanism which draws a continuous tow of filamentary filter material from a bale and transports the tow lengthwise through an impregnating station where the filaments are contacted by particles of a liquid plasticizer or softening agent. Prior to entering the impregnating station, the tow is caused to pass through one or more so-called banding devices wherein the tow is converted into a layer so as to expose all or nearly all of its filaments during travel through the impregnating station. The impregnated layer is thereupon advanced through a gathering device (called horn) which converts the layer into a rod-like filler ready to be wrapped into a web of cigarette paper, imitation cork or other suitable wrapping material to thus complete the conversion of the tow and wrapping material into a continuous wrapped filter rod. The filter rod is severed at regular intervals to yield filter rod sections or plugs of unit length or multiple unit length. The tow normally consists of cellulose acetate fibers and the purpose of the plasticizer is to soften portions on the surface of each filament so that the thus softened portions adhere to each other and form an integral network of filaments which defines a maze of paths for tobacco smoke.
It is already known to supply plasticizer to the impregnating station at a rate which is proportional to the rate of transport of the layer of filamentary material. It is also known to employ a rotating brush as a means for atomizing the plasticizer and for propelling the particles of atomized plasticizer against one side of the moving layer of filamentary filter material at the impregnation station. Reference may be had to the Defensive Publication No. T874,005 of Fritz et al. published May 19, 1970. A drawback of presently known atomizing apparatus is that the application of atomized plasticizer is not uniform. The published article discloses an apparatus wherein a roller dips into a supply of liquid plasticizer and withdraws a film which is advanced into the range of bristles on a rotating brush. The latter propels particles of plasticizer against the moving layer of filter material. The uniformity or lack of uniformity of atomizing and plasticizer applying action depends on a number of unpredictable factors including the height of the supply of liquid plasticizer, the speed at which the roller and the brush rotate and certain others.